Dead branches in the open source tree

To prune or merge, that is the question.

Dead branches

One of the great things about open source software, in particular free (in the truest sense) software, is that once you have the source for a project that comes very close to meeting your needs, you can bootstrap your application with code from that project. Many who do this donate their code back to the community, but there are also many who don't.

Those who don't contribute back into the community, and who don't continuously integrate their custom code with the OSS project source can find themselves with a dead branch. A dead branch isn't necessarily a catastrophe: Except for the odd security vulnerability, many sites run without code changes for years. But for a vibrant growing site, the cost of developing the core application as well as your modifications can be so great that it's simply ignored.

Merge and merge often

Through good, modular design and regular merging with the OSS project trunk it's often possible to avoid creating a dead branch whilst simultaneously taking advantage of the often rich contributions and enhancements of the OSS community.

I wonder though, is this against the spirit of open source? Or is it simply making good use of free software? Or a bit of both?